Fever Not a Reliable Indicator of Influenza (A) H1N1 Infection

WASHINGTON, DC -- July 29, 2010 -- Individuals infected with mild influenza (A) H1N1 may go undetected using standard diagnostic criteria, according to a study in the August issue of the American Journal of Infection Control, the official publication of the Association for Professionals in Infection Control and Epidemiology (APIC).

The study concludes that coughing or other respiratory symptoms are more accurate in determining influenza infection than presence of a fever.

Currently, public health officials rely on detecting fever to screen individuals for potential infection with H1N1. During a pandemic, for example, standard screening at airports relies on body-temperature scanners to detect the presence of fever.

The study's authors found, however, that coughing, not fever, is a more reliable indicator of infection, because nearly half of the individuals with mild infection may not have fever.

A team led by Sang Won Park, MD, Seoul National University, Seoul, South Korea, investigated confirmed cases of H1N1 who were hospitalised and quarantined during the early stages of the pandemic in 2009. The results demonstrated that only 45.5% of the case subjects had fever.

Individuals with mild infection and no fever have the potential to evade detection at airports or medical triage units, thus continuing the chain of infection.

"Our study found that fever is not reliable for case definition, even though it has been regarded as a key factor in determining influenza infection," said Dr. Park. "We are aware of other studies that show fever present in as few as 31% of confirmed cases of influenza. We found that the most sensitive indicator was cough."

Dr. Park adds that "screening should take any kind of respiratory manifestation into account."

SOURCE: American Journal of Infection Control